A number of inorganic compounds, described herein as acid chlorides have wide utility. Examples of these materials include magnesium chloride, aluminium chloride, silicon chloride, phosphorus chloride and stannous chloride. A common feature for these materials, with the exception of magnesium chloride, is that when in contact with water they dissociate and liberate hydrochloric acid. The basic reactions are summarised below:    Dissolution of Magnesium Chloride in water:MgCl2(s)+6H2O(l)→[Mg(H2O)6]2+(aq)+2Cl−(aq) [Mg(H2O)6]2+(aq)+H2O(l)[Mg(H2O)5(OH)]+(aq)+H3O+(aq)     Reaction of Aluminium Chloride with water:AlCl3(s)+3H2O(l)→[Al(OH)3](s)+3HCl(g)     Reaction of Phosphorous (V) Chloride with water:PCl5+H2O→POCl3+2HCl    Reaction of Stannous Chloride with water:SnCl2+H2O→Sn(OH)Cl+HCl
The above acid chlorides can be incorporated into polymer processing by means of first producing a so-termed masterbatch. A masterbatch is a high concentration combination of a base polymer with an additive, such as the aforementioned acid chlorides. A masterbatch may then be introduced into a further polymer production process so as to liberate the additive, so as to, for example, initiate a chemical reaction.
A masterbatch is typically produced by contacting a molten resin or polymer with the required additives in the correct concentration before mixing, and subsequently the mixture is extruded to form solid pellets. The aim of the process is to provide pellets with a uniform concentration of additive dispersed through them; the pellets can be easily handled by plastics manufacturers and incorporated into their production. Production may be batchwise or continuous depending on the equipment and volume. When dealing with chemically reactive masterbatch components, such as the acid chlorides, it is preferable that the masterbatch is primarily a mixture of a relatively unreactive polymer, such as polyethylene or polypropylene, even if this polymer is not the primary polymer into which the masterbatch is subsequently incorporated.
One specific example of a reactive masterbatch using an acid chloride is in the polymerisation of rubbers, such as EPDM rubber in which a masterbatch comprising stannous chloride is introduced. This facilitates cross-linking between molecules in order to obtain desired properties. The incorporation of stannous chloride in a masterbatch is described in patent GB 2489123, and the use of a stannous chloride masterbatch as the catalyst in curing thermoplastic vulcanisate in WO2011081746. Aluminium chloride is used as a catalyst in rubber production, as taught by the patents RU2337111 and RU2439084.
The use of a masterbatch as mentioned above has utility in that a friable and potentially dusty acid chloride can be entrained in the masterbatch polymer and its availability to the environment reduced. This is particularly useful in reducing dusting and general handleability improvement. However, as mentioned previously the purpose of a masterbatch is to introduce an additive in a high concentration form into a further process. It is therefore generally disadvantageous to incorporate more masterbatch polymer (the polymer primarily constituting the masterbatch) than absolutely necessary. However, as increasing loadings of additive, such as the acid chloride, are included in the masterbatch the ability of the masterbatch polymer to fully encapsulate the additive reduces.
An ongoing problem with masterbatch comprising acid chlorides is that when contacted with water, such as moisture from the hands of a person handling the masterbatch, acid can be released and this has a corrosive effect leading to health and safety problems. By example, a stannous chloride masterbatch as described earlier remains corrosive and is classified as such for transport, resulting in additional handling costs.
It is therefore one object of the present invention to provide an acid chloride masterbatch having reduced corrosivity.
A further issue with high loading of additive in a masterbatch is that a masterbatch is typically provided as a pelletised material, such as an extrudate which is chopped into pellets, one example being an extrudate chopped into pellets at increased temperature so as to give a degree of spheronisation to the masterbatch. It is generally advantageous that masterbatch particles and particles in general for polymerisation should be monodisperse and additionally spherical. A mono dispersed particle is less likely to give rise to flow problems and particle segregation. Spherical particles also provide improved flow.
It is therefore a further object of the present invention to provide a masterbatch having improved flow characteristics.
Problems addressed by the present invention therefore include: the dust formation that is typically a hazard when loading inorganic chloride powders into vessels is reduced, the corrosiveness of the product is reduced, and finally the product can be easily introduced into resin, polymer, and plastics production at the correct dosage, in a form that is readily mixed with the other components.
The immobilisation of acid chlorides more generally is known.
Chinese patent CN102658179, discloses a preparation method of stannous chloride immobilized catalyst, teaches a better method of immobilizing stannous chloride onto an inorganic porous carrier in order for it to be used as a catalyst in fixed bed reactions. The patent describes how to fix the gaseous stannous chloride onto the porous inorganic support. Although this patent teaches how to reduce the corrosiveness of this catalyst, the end use is not in the same field and the catalyst is fixed onto an inorganic porous structure rather than into an organic polymer matrix as in the current application.
The present invention provides a coated inorganic acid chloride having an organosilane coating such as derived by reacting the inorganic acid chloride reacted with an organosilane.